Monocrystalline AlN Etch Stop Layers for Low-Temperature BEOL Reliability
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Solution Overview
Problem
Integrated circuit fabrication faces challenges with reliability issues due to damage during etching processes, particularly when exceeding maximum temperature limits in back-end-of-line processes, which can adversely affect semiconductor devices.
Innovation Solution
The use of a monocrystalline aluminum nitride layer formed through atomic layer deposition (ALD) with a plasma treatment at temperatures below 425°C, converting polycrystalline aluminum nitride into monocrystalline phase to serve as etch stop and liner layers, ensuring compatibility with BEOL process constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching processes are used in integrated circuit fabrication, then manufacturing progress can be maintained, but reliability issues occur due to damage during etching processes
Solution Approach 1:
The patent applies preliminary action by forming a protective liner layer and etch stop layer before performing etching operations. The liner layer is deposited on metal interconnect structures prior to dielectric layer formation, and the etch stop layer is formed on the base structure before trench etching. These pre-formed protective layers prevent damage to underlying structures during subsequent etching processes, thereby maintaining reliability while enabling continued manufacturing progress.
2Ease of manufacture
If temperature exceeds maximum limit in back-end-of-line processes, then certain processing operations can be performed, but semiconductor devices are undesirably damaged
Solution Approach 1:
The patent applies parameter changes by carefully controlling deposition temperatures to remain at or below 425°C during back-end-of-line processing. The atomic layer deposition process is specifically configured to operate within this temperature constraint, allowing formation of dielectric layers and protective coatings without exceeding the maximum temperature limit that would damage previously formed semiconductor devices. This enables continued manufacturing capability while preserving device integrity.
3Ease of manufacture
If polycrystalline aluminum nitride is used as etch stop layer, then manufacturing is simpler, but thermal conductivity is insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the crystal structure of aluminum nitride from polycrystalline to monocrystalline phase through controlled atomic layer deposition. The deposition process parameters are specifically optimized to promote monocrystalline growth, achieving significantly enhanced thermal conductivity compared to conventional polycrystalline aluminum nitride. This resolves the contradiction by maintaining manufacturing feasibility while dramatically improving the thermal management capability of the etch stop layer.
4Reliability
If liner layer thickness is increased, then metal protection from oxidation is improved, but capacitance and contact resistance increase
Solution Approach 1:
The patent applies parameter changes by optimizing the liner layer thickness to a specific range that balances protection and electrical performance. The liner layer is deposited at controlled thicknesses (typically 1-10 nanometers) using atomic layer deposition, providing sufficient oxidation protection to metal interconnects while maintaining low capacitance and contact resistance. This precise thickness control resolves the contradiction by achieving adequate protection without introducing harmful electrical effects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The monocrystalline aluminum nitride layers provide enhanced thermal conductivity, protect metals from oxidation, reduce capacitance and contact resistance, and maintain low thickness, thereby improving the reliability and performance of semiconductor structures.
Implementation Method 1
forming a plurality of atomic layers which cover an inner surface of the trench and which serve as a liner; and forming a metal contact in the trench
Implementation Method 2
converting polycrystalline aluminum nitride into monocrystalline phase to serve as etch stop and liner layers
Implementation Method 3
formed through atomic layer deposition (ALD) with a plasma treatment at temperatures below 425°C
Data Source
AI summary
A method for manufacturing a semiconductor structure includes: forming a dielectric layer on a base structure; forming a trench in the dielectric layer to expose the base structure; forming a metal contact in the trench; and performing a plurality of first atomic layer deposition (ALD) cycles to form a plurality of first atomic layers which cover the dielectric layer and the metal contact and which serve as an etch stop layer. Each of the first ALD cycles includes: forming a corresponding one of the first atomic layers; and performing a treatment to convert the corresponding first atomic layer into monocrystalline phase at a temperature not greater than 425° C.